Asphaltenes are a major component in crude oil, and there is general agreement as to the deleterious effects of asphaltenes in the reduction of oil extraction and processing in the petrochemical industry. Asphaltenes can deposit in the pores of formations, blocking the flow of fluids. Additionally, asphaltenes can precipitate from a stream of oil and coat boreholes, production tubing, and transport lines. Moreover, in a processing facility, asphaltenes can foul processing equipment and poison catalysts.
Asphaltene molecules have been widely reported as having a fused polyaromatic ring system and containing heteroatoms such as sulfur, oxygen, nitrogen, and the like. The heteroatoms may be part of the aromatic ring system or part of other carbocyclic rings, linking groups, or functional groups. Two structural motifs for asphaltene molecules are the so-called continental and archipelago structures. In the continental structure, alkyl chains connect to and branch from a central polyaromatic ring system, which is believed to contain several fused aromatic rings, e.g., 5 or more aromatic rings. In the archipelago structure, multiple polyaromatic ring systems are connected by alkyl chains that may contain a heteroatom, and additional alkyl chains extend freely from the polyaromatic rings. The number of fused aromatic rings in the continental structure can be greater than the number of fused aromatic rings in the archipelago structure.
In addition to the aromatic regions of the asphaltenes, heteroatoms provide the asphaltenes with polar regions, and the terminal alkyl chains provide hydrophobic regions. Consequently, it is believed that asphaltene molecules aggregate into various micellular structures in oil, with the alkyl chains interacting with the aliphatic oil components. Resin from the oil can insert between aromatic planes of neighboring asphaltene molecules in asphaltene aggregates, aiding in maintaining their micellular structure. Asphaltenes can precipitate from oil in structures where asphaltene molecules form stacked layers having aligned aromatic regions and aligned aliphatic regions.
Materials and methods for treating and removal of asphaltenes from oil environments such as a reservoir would be well received in the art.